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AS Biology > Definitions:Topic 2 > Flashcards

Definitions:Topic 2 Flashcards

1
Q

What is a cell membrane?

A

The selectively permeable membrane which surrounds the cytoplasm of a cell, acting as a barrier between the cell
contents and their surroundings

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2
Q

Define organelles.

A

sub-cellular bodies found in the cytoplasm of cells

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3
Q

What are enzymes?

A

Proteins that act as biological catalysts for a specific reaction or group of reactions

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4
Q

What are vesicles?

A

Membrane ‘bags’ that hold secretions made in cells

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5
Q

Define phospholipids.

A

Chemicals in which glycerol bonds with two fatty acids and an inorganic phosphate group

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6
Q

What are polar lipids?

A

Lipids with one end attached to a polar group (e.g. a phosphate group) so that one end of the molecule is hydrophilic and one end is hydrophobic

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7
Q

Define hydrophilic.

A

A substance with an affinity for water that will readily dissolve in or mix with water

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8
Q

Define hydrophobic.

A

A substance that tends to repel water and that will not mix with or dissolve in water

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9
Q

Define a monolayer.

A

A single closely packed layer of atoms or molecules

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10
Q

What are micelles?

A

A spherical aggregate of molecules in water with hydrophobic areas in the middle and hydrophilic areas outside

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11
Q

What is a bilayer?

A

A double layer of closely packed atoms or molecules

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12
Q

What is a unit membrane?

A

A lipoprotein membrane which is composed of two protein layers enclosing a less dense lipid

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13
Q

Define the fluid mosaic model.

A

The current model of the structure of the cell membrane including floating proteins forming pores, channels and
carrier systems in a lipid bilayer

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14
Q

What are gated channels?

A

Protein channels through the lipid bilayer of a membrane that are opened or closed, depending on conditions in the cell

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15
Q

What are glycoproteins?

A

Conjugated proteins with a carbohydrate prosthetic group

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16
Q

Define passive transport.

A

Transport that takes place as a result of concentration, pressure or electrochemical gradients and involves no energy from a cell

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17
Q

Define active transport.

A

The movement of substances into or out of the cell using ATP which is produced during cellular respiration

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18
Q

Define diffusion.

A

The movement of the particles in a liquid or gas down a concentration gradient from an area where they are at a relatively high concentration to an area where they are at a relatively low concentration

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19
Q

Define facilitated diffusion.

A

Diffusion that takes place through carrier proteins or protein channels

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20
Q

Define osmosis.

A

A specialised form of diffusion that involves the movement of solvent molecules down their water
potential gradient

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21
Q

Define partially permeable membrane.

A

A membrane which only allows specific substances to pass through it

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22
Q

What is a solute.

A

A substance in a solution, dissolved in the solvent

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23
Q

What is a carrier protein?

A

A protein that moves a substance through the membrane in active transport using energy from the breakdown of ATP or in passive transport such as facilitated diffusion down a concentration gradient

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24
Q

Define endocytosis.

A

The movement of large molecules into cells through vesicle formation

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25
Q

Define exocytosis.

A

The movement of large molecules out of cells by the fusing of a vesicle containing the molecules with the surface cell membrane; the process requires ATP

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26
Q

What is water potential?

A

A measure of the potential for water to move out of a solution by osmosis

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27
Q

What is osmotic concentration?

A

A measure of the concentration of the solutes in a solution that have an osmotic effect

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28
Q

What is an isotonic solution?

A

A solution in which the osmotic concentration of the solutes is the same as that in the cells

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29
Q

What is a hypotonic solution?

A

A solution in which the osmotic concentration of solutes is lower than that in the cell contents

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30
Q

What is a hypertonic solution?

A

A solution in which the osmotic concentration of solutes is higher than that in the cell contents

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31
Q

Define hydrostatic pressure.

A

The pressure exerted by a fluid in an equilibrium

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32
Q

Define turgor.

A

The state of a plant cell when the solute potential causing water to be moved into the cell by osmosis is balanced by the force of the cell wall pressing on the protoplasm

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33
Q

Define incipient plasmolysis.

A

The point at which so much water has moved out of the cell by osmosis that turgor is lost and the cell membrane begins to pull away from the cell wall as the protoplasm shrinks

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34
Q

Define plasmolysis.

A

The situation when a plant cell is placed in hypertonic solution when so much water leaves the cell by osmosis that the vacuole is reduced and the protoplasm is concentrated and shrinks away from the cell walls

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35
Q

What is ATPase?

A

An enzyme that catalyses the hydrolysis of ATP, releasing energy to move carrier systems and drive metabolic reactions

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36
Q

What is a cyanide?

A

A metabolic poison that stops mitochondria working

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37
Q

What is phagocytosis?

A

The active process when a cell engulfs something relatively large such as a bacterium and encloses it in a vesicle

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38
Q

What is pinocytosis?

A

The active process by which cells take in tiny amounts of extracellular fluid by tiny vesicles

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39
Q

What is a lung surfactant?

A

A special phospholipid that coats the alveoli and prevents them from collapsing

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40
Q

Define breathing (ventilation)?

A

The process in which physical movements of the chest change the pressure so that air is moved in or out

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41
Q

What is inhalation?

A

Breathing in

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42
Q

What is exhalation?

A

Breathing out

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43
Q

What are pathogens?

A

Microorganisms that cause disease

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44
Q

What is a catalyst?

A

A substance that speeds up a reaction without changing the substances produced or being changed itself

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45
Q

What are enzymes?

A

A proteins that act as biological catalysts for a specific reaction or group of reactions

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46
Q

Define specificity.

A

The characteristic of enzymes that means that each enzyme will catalyse only a specific reaction or group of reactions; this is due to the very specific shapes which come from the tertiary
and quaternary structures

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47
Q

What are anabolic reactions?

A

A reaction that builds up (synthesises) new molecules in a cell

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48
Q

What are catabolic reactions?

A

A reaction which breaks down substances within a cell

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49
Q

Define metabolism.

A

The sum of the anabolic and catabolic processes in a cell

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50
Q

Define a metabolic(metabolic pathway).

A

A series of linked reactions in the metabolism of a cell

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51
Q

What are intercellular enzymes?

A

Enzymes that catalyse reactions within the cell

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52
Q

What are extracellular enzymes?

A

Enzymes that catalyse reactions outside of the cell in which they were made

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53
Q

What is activation energy?

A

The energy needed for a chemical reaction to get started

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54
Q

What is a substrate?

A

The molecule or molecules on which an enzyme acts

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55
Q

Define the lock-and-key hypothesis.

A

A model that explains enzyme action by an active site in the protein structure that has a very specific shape; the enzyme and substrate slot together to form a complex in the same way as a
key fits in a lock

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56
Q

What is the active site?

A

The area of an enzyme that has a specific shape into which the substrate(s) of a reaction fit

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57
Q

Define induced-fit hypothesis.

A

modified version of the lock-and-key model of enzyme action where the active
site is considered to have a more flexible shape; after the substrate enters the active site, the shape of that site changes around it to form the active complex; after the products have left the complex, the enzyme returns to its inactive, relaxed form

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58
Q

Define molecule number(turnover number).

A

The number of substrate molecules transformed per minute by a single enzyme molecule

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59
Q

Define temperature coefficient(Q10).

A

The measure of the effect of

temperature on the rate of a reaction

60
Q

What is denaturation?

A

The loss of the three-dimensional shape of a protein (e.g. caused by change in temperature or pH)

61
Q

What is the initial rate of reaction?

A

The measure taken to compare the

rates of enzyme-controlled reactions under different conditions

62
Q

What are mononucleotides?

A

Molecules with three parts- a 5-carbon pentose sugar; a nitrogen-containing base and a phosphate group - joined by condensation reactions

63
Q

What is adenosine triphosphate (ATP)?

A

A molecule that acts as the universal energy supply. molecule in cells, inti
made up of the base adenine, the pentose supar ribose and three phosphate groups

64
Q

Define deoxyribonucleic acid (DNA).

A

A nucieic acid that is the genetic material in many organisms

65
Q

What is ribonucleic acid(RNA)?

A

A nucleic acid which is the genetic material in some organisms and is involved in protein synthesis

66
Q

What is a ribose?

A

A pentose sugar that is part of the structure of RNA

67
Q

What is deoxyribose?

A

A pentose sugar that is part of the structure of DNA

68
Q

What is a purine base?

A

A base found in nucleotides that has two nitrogen-containing rings

69
Q

What is a pyrimidine base?

A

A base found in nucleotides that has one nitrogen-containing ring

70
Q

Define adenine.

A

A purine base found in DNA and RNA

71
Q

Define guanine.

A

A purine base found in DNA and RNA

72
Q

Define cytosine.

A

A pyrimidine base found in DNA and RNA

73
Q

Define thymine.

A

A pyrimidine base found in DNA

74
Q

Define uracil.

A

A pyrimidine base found in RNA

75
Q

What are nucleic acids/polynucleotides?

A

Polymers made up of many nucleotide monomer units that carry all the information needed to form new cells

76
Q

What is a phosphodiester bond?

A

Bond formed between the phosphate group of one nucleotide and the sugar of the next nucleotide in a condensation reaction

77
Q

What are complementary base pairs?

A

Complementary purine and pyrimidine bases which align in a DNA helix, with hydrogen bonds holding them together (C-G,A-T)

78
Q

What is a genome?

A

The entire genetic material of an organism

79
Q

What is conservative replication?

A

A model of DNA replication which suggests that the original double helix remains intact and in some way instructs the formation of a new, identical double helix made up entirely of new material

80
Q

What is semiconservative replication?

A

The accepted model of DNA replication in which the DNA ‘unzips’ and new nucleotides align along each strand;each new double helix contains one strand of the original DNA and one strand made up of new material

81
Q

What are isotopes?

A

Different atoms of the same element, with the same number of protons but a different number of neutrons; isotopes have the same chemical properties

82
Q

Define DNA helicase.

A

An enzyme involved in DNA replication that ‘unzips’ the two strands of the DNA molecules

83
Q

Define DNA polymerase.

A

An enzyme involved in DNA replication that lines up the new nucleotides along the DNA template strands

84
Q

Define DNA ligase.

A

An enzyme involved in DNA replication that catalyses the formation of phosphodiester bonds between the nucleotides

85
Q

What is translation?

A

The process by which proteins are produced, via RNA, using the genetic code found in the DNA; it takes place in the ribosomes

86
Q

What are ribosomes?

A

The site of protein synthesis in the cell

87
Q

What is a triplet code?

A

The code of three bases that is the basis of the genetic information in the DNA

88
Q

What is a gene?

A

A sequence of bases on a DNA molecule; it contains coding for a sequence of amino acids in a polypeptide chain that affects a characteristic in the phenotype of the organism

89
Q

What is a codon?

A

A sequence of three bases in DNA or mRNA

90
Q

Define messenger RNA(mRNA).

A

The RNA formed in the nucleus that carries the genetic code out into the cytoplasm

91
Q

What is a complementary strand?

A

The strand of RNA formed that complements the DNA acting as the coding strand

92
Q

What is the non-overlapping code?

A

A code where each codon codes for only one thing with no overlap between codons

93
Q

What is a degenerate code?

A

A code containing more information than is needed

94
Q

Define point mutation.

A

A change in a single base of the DNA code

95
Q

What is a sense strand?

A

The DNA strand that carries the code for the protein to be produced

96
Q

What is an antisense strand(template strand)?

A

The DNA strand which acts as a template for an mRNA molecule

97
Q

What is a start codon?

A

The sequence of bases which indicates the start of an amino acid chain

98
Q

What is RNA polymerase?

A

The enzyme that polymerises nucleotide units to form RNA in a sequence determined by the antisense strand of DNA

99
Q

What is a stop codon?

A

One of three sequences of bases which indicate the end of an amino acid chain

100
Q

Define transfer RNA(tRNA).

A

Small units of RNA that pick up specific amino acids from the cytoplasm and transport them to the surface of the
ribosome to align with the mRNA

101
Q

Define the term anticodon.

A

A sequence of three bases on tRNA that are complementary to the bases in the mRNA codon

102
Q

Define translation.

A

The process by which the DNA code is converted into a protein from the mRNA strand made in the nucleus

103
Q

Define transcription.

A

The process by which the DNA sequence is used to make a strand of mRNA in the nucleus

104
Q

What are polysomes?

A

Groups of ribosomes, joined by a thread of mRNA, that can produce large quantities of a particular protein

105
Q

Define mutation.

A

A permanent change in the DNA of an organism

106
Q

What are gametes?

A

Haploid sex cells that fuse to form a new diploid cell (zygote) in sexual reproduction

107
Q

What is point mutation(gene mutation)?

A

A change in a single base of the DNA code

108
Q

What is substitution?

A

A type of point mutation in which one base in a gene is substituted for another

109
Q

What is deletion?

A

A type of point mutation in which a base is completely lost

110
Q

What is insertion?

A

A type of point mutation in which an extra base is added into a gene, which may be a repeat or a different base

111
Q

What are chromosomal mutations?

A

Changes in the position of entire genes within a chromosome

112
Q

What are whole-chrosomal mutations?

A

The loss or duplication of a whole chromosome

113
Q

Define variation.

A

Differences between organisms which may be the result of different genes or the environment they live in

114
Q

What is a mutagen?

A

Anything that increases the rate of mutation

115
Q

Define the term phenotype.

A

The physical traits, including biochemical

characteristics, expressed as a result of the interactions of the genotype with the environment

116
Q

Define the term genotype?

A

The genetic make-up of an organism with respect to a particular feature

117
Q

What are homologous pairs?

A

Matching pairs of chromosomes in an

individual which both carry the same genes, although they may have different alleles

118
Q

Define the term locus.

A

The site of a gene on a chromosome

119
Q

Define the term allele.

A

Versions of a gene, variants

120
Q

Define homozygote.

A

An individual where both alleles coding for a particular characteristic are
identical

121
Q

Define heterozygote.

A

An individual where the two alleles coding for a particular characteristic are
different

122
Q

What does the term ‘dominant’ mean?

A

A characteristic which is expressed in the

phenotype whether the individual is homozygous or heterozygous for that allele

123
Q

What does th term ‘recessive’ mean?

A

A characteristic which is only expressed when both alleles code for it; in other words, the individual is homozygous for the recessive trait

124
Q

What is true breeding?

A

Homozygous organism which will always
produce the same offspring when crossed with another organism for the
same characteristic

125
Q

Define monohybrid.

A

A genetic cross where only one gene for
one characteristic is considered codominance in heterozygotes, where both alleles at a gene locus are fully expressed in the phenotype

126
Q

Define sex-linked traits.

A

Characteristics which are inherited on the sex chromosomes

127
Q

What are autosomes?

A

Chromosomes which carry information about the body but do not determine the sex of an individual

128
Q

Define homogametic.

A

An individual who produces gametes that contain only one type of sex chromosome - in humans this is the female

129
Q

Define heterogametic.

A

An individual who produces two types of gamete each containing different types of sex chromosome - in humans this is the male

130
Q

What are transcription factors?

A

Proteins that bind to the DNA in the nucleus and affect the process of converting or transcribing DNA into RNA

131
Q

Define epigenetics.

A

The study of changes in gene expression (active versus inactive genes) that does not involve changes to the underlying DNA sequence but affects how cells read genes

132
Q

Define sex-linked diseases.

A

Genetic diseases that result from a mutated gene carried on the sex chromosomes - in human beings, on the X chromosome red-green colour blindness, a sex-linked genetic condition which affects the ability to distinguish tones of red and green

133
Q

Define haemophilia.

A

A sex-linked genetic disease in which one of the factors needed for blood to clot is not made in the body

134
Q

What is cystic fibrosis(CF)?

A

A serious genetic disease caused by a recessive allele which affects the production of mucus by epithelial cells

135
Q

What are exocrine glands?

A

Glands which produce substances and secrete them to where they are needed through a small tube called a duct

136
Q

Define villi.

A

Finger-like projections of the lining of the duodenum and small intestine which increase the surface area for the absorption of digested food

137
Q

What is the duodenum?

A

The first part of the gut after the stomach

138
Q

What is the pancreatic duct?

A

The duct from the pancreas which carries digestive enzymes made in the pancreas into the duodenum

139
Q

What is insulin?

A

Hormone made in the pancreas involved in the regulation of blood sugar levels

140
Q

What is genetic screening?

A

When whole populations are tested for a genetic disease

141
Q

What is phenylketonuria(PKU)?

A

A recessive genetic disorder where those affected lack the enzyme needed to digest the amino acid phenylalanine; the amino acid builds up in the blood and causes severe brain damage

142
Q

What is prenatal screening?

A

Screening of an embryo or fetus before birth

143
Q

What is amniocentesis?

A

A type of prenatal screening which involves removing a sample of amniotic fluid at around 16 weeks of pregnancy, culturing the fetal cells found and analysing them for genetic diseases

144
Q

What is chrionic villus sampling?

A

A type of prenatal screening where a small sample of embryonic tissue is taken from the developing placenta and the cells tested for genetic diseases

145
Q

What is preimplantation genetic diagnosis?

A

Testing the cells of an embryo produced by IVF to check for genetic diseases before it is implanted into the uterus of the mother

AS Biology (6 decks)

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